In the high end semiconductor industry, machine positioning stages (also called positioning devices) are present which perform various functions. Guiding of these stages cannot be done in a conventional way (e.g. by use of ball bearing guides) due to vacuum and contamination requirements. Also other types of bearings (e.g. gas bearings) are difficult to use in such an environment.
Stages with contactless guidings based on magnetic forces seem very suitable for these types of applications. Commonly these types of stages are designed with six actuators, one for each degree of freedom. However, this increases the complexity and cost of the system hardware.
WO 2005/026801 A2 discloses an apparatus for manipulation of an optical element in up to six degrees of freedom with respect to a structure via at least three actuator devices. Each actuator device has at least two force-controlled actuators, which each produce an effective force along one degree of freedom, with linking points of the actuator devices acting directly on the optical element.